Quinazoline ring system constituting a class of antihypertensive agents is well known in the art. Prazosin disclosed in U.S. Pat. No. 3,511,836, a 2-substituted quinazoline derivative, has been proven effective in the clinic acting as an .alpha..sub.1 -adrenoceptor antagonist.
U.S. Pat. No. 4,335,127 discloses 3-substituted quinazolines such as ketanserin, thioketanserin which have been found being potent serotonin-antagonists.
In an article entitled "Further Evaluation of the Selectivity of a Novel Antihypertensive agent, SGB-1534, for Peripheral .alpha.1-adrenoceptors in the Spinally Anesthetized Dog" Eur. J. Pharmacol. 1986, 131, 257-264, Junichi Imagawa et al. disclose SGB-1534, a 3-substituted quinazoline derivative, which also have been proven to have antihypertensive activities by an .alpha..sub.1 -adrenoceptor antagonist.
As a result of an extensive investigations to develop a more potent and clinically effective antihypertensive agent, a novel series of imidazo[1,2-c]quinazolinone derivatives, 2-substituted methyl-2,3-dihydroimidazo[1,2-c]quinazolin-5(6H)-ones (-thiones), have been newly synthesized in the present invention.
Accordingly, one object of the present invention is to provide new and useful 2-substituted methyl-2,3-dihydroimidazo[1,2-c]quinazolin-5(6H)-ones (-thiones) and pharmaceutically acceptable salts thereof.
Another object of the present invention is to provide a process for preparing the 2-substituted methyl-2,3-dihydroimidazo[1,2-c]quinazolin-5(6H)-ones (-thiones) and pharmaceutically acceptable salts thereof.
A further object of the present invention is to provide a pharmaceutical composition containing, as an active ingredient, the 2-substituted methyl-2,3-dihydroimidazo[1,2-c]quinazolin-5(6H)-ones (-thiones) or a pharmaceutically acceptable salt thereof.
Still another object of the present invention is to provide a method for the treatment of high blood pressure comprising administrating to a mammal in need of said treatment an effective amount of the 2-substituted methyl-2,3-dihydroimidazo-[1,2-c]quinazolin-5(6H)-ones (-thiones) or a pharmaceutically acceptable salt thereof.